The guy I bought the carb from stated that the port in question had to be hooked up to a external vacuum source. The vacuum does not come internally through the carb. Otherwise it won't run right. Something to do with a power valve that requires vacuum. It's been a while.

Chuck that sounds right, but I would go to a Turbo Buick site and post there. I know that draw through carbs have power valve issues, do to constant vacuum from the blower/turbo. That is one of the many reasons for failed home turbo swaps. The gang on the blown/turbo car forums have had to deal with this and know much more than I on the subject, as soon as I win the lottery I will commence a learnin' 'cause I WANT a blower! Harry

I'm not a hoarder I'm a preservationist 78 Monza Spyder (Soon To Be 2+2 with Spoilers)

I've put the carb for sale in the for sale section if anyone is interested. It looks as if the pevr valve is an unobtanium 1 yr. only part unless someone else knows different. This is a good carb. I would hate for it to be wasted. I've purchased a '79 Corvette q-jet off ebay. Change the jets and adjust the secondary for less airflow should do it after a good rebuild.